The idea that motion (the phenomenon, the tangible reality) occurs and renders the definitions on the substance (the medium of motion) within the volumetric space dimension and the idea that duration (a noumenon, an abstract reality) occurs and renders the definition of the instance through the time dimension used to be the simple fundamentals.

But these ideas are now terribly confused in the present day explanations.

In the present day explanations, the space dimension is no longer just the container, no longer the essence that gets occupied; it has now been argued that space is also the substance of the existence, the medium for the motion; the old meaning for the word "space" that conveys the simple idea of that essence that gets occupied by the substance is now almost discarded.

In the present day explanations, the time dimension is no longer the separate dimension in which duration occurs and renders the definition of the instance of the existence. There has actually been a long standing confusion regarding time. Indeed, we have time, the dimension, time, the duration, and time, the instance of existence. The word "time" has actually been of confused meaning for a very long time. And this confusion regarding time has been further confused by the idea of a space-time continuum.

In the present day explanations, the idea regarding motion and the idea regarding duration are now very much confused. The idea of the space dimension and the idea of the time dimension are now also very much confused. And the present day explanations also confuse the ideas regarding "substance" and "instance".

Nevertheless, the idea that duration and motion are two different realities that occur in the separate space and time dimensions apparently remains. The simple idea is that duration occurs and motion occurs. Both simply occur and they never cease to occur; they are coexisting fundamental realities. They occur in unison.

Motions interact with other motions to effect kinematic transformations for the tangible reality rendered in the substance of existence. And duration simply flows and renders the definition of the instance of existence. But motion cannot interact with duration in a manner that effects transformations on each other, since one is fundamentally the tangible reality and the other is purely an abstract reality devoid of fundamental tangibility.

Although it has its intangible abstract representations, motion is fundamentally tangible - a phenomenon. And although it has its tangible representations in clocks, duration is fundamentally abstract - a noumenon.

The idea remains that motion renders the definition of mass and energy on the substance that occupies the volumetric space dimension. The idea that "motion is the underlying essence of mass and energy" is clearly the simple suggestion. Thus, mass is a construct of motion and energy is a construct of motion.

It appears that motion (the tangible phenomenon) is gathered up into the gravitational domains as duration (an abstract noumenon) occurs.

Gravitation is a perpetual motion that occurs around gravitational domains. The gravitational field around gravitational domains is a continuous occurrence. Thus, the gravitational domains increase in their motion (mass-energy) content.

A big question is that regarding where the motions that define the gravitational field come from. What is the origin of gravitation?

The theory of kinematic relativity provides an answer to this big question.